The present invention pertains generally to signal generators and more specifically to radar antenna pattern generators. In general, radar simulations are used to evaluate the performance of electronic countermeasures equipment and other testing devices. Two different types of antenna patterns are generated in these simulations. The first of these, the free-running scan pattern, is used in open-loop testing to evaluate receivers. Presently, three methods are employed to obtain these scan patterns. The first of these methods utilizes sine waves and pulse generators to provide crude simulations. A second method uses tape recordings of replicas of scan patterns which provide high quality simulation of particular radar transmissions but require expensive FM tape recorders and the added expense incurred for field operations in producing the tapes. The third method utilizes commercial pattern generators which provide generic type patterns typical of standard radar transmissions but do not provide simulations for any particular pattern.
The second type of antenna pattern generated is used in closed-loop tests to evaluate total performance of countermeasures equipment under laboratory conditions. Two methods are presently used to produce these closed-loop antenna patterns. The first method utilizes diode function generators associated with analog computers. The second method uses a photoformer flying spot scanner in conjunction with the photographic plates of the particular pattern to be generated. Both methods provide a fairly high quality antenna pattern as a function of an analog antenna sweep function. However, the reliability has been inconsistent and the production of photographic slides of the particular patterns to be generated has been expensive. Additionally, the added costs of an oscilloscope and a photo multiplier tube are required in the photoformer flying spot scanner technique.